Field of the Invention
The present disclosure relates to a memory protection device and method and an organic light emitting display device including the same.
Discussion of the Related Art
An active matrix type organic light emitting display device includes a self-luminous organic light emitting diode (OLED) and has many advantages such as fast response speed, high emission efficiency, high luminance, and wide viewing angle.
An OLED typically includes an anode electrode, a cathode electrode, and organic compound layers (hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL)) formed therebetween. The organic compound layers include the HIL, HTL, EML, ETL, and EIL. When a driving voltage is applied between the anode electrode and the cathode electrode, holes which have passed through the HTL and electrons which have passed through the ETL move to the EML to form excitons, resultantly causing the EML to emit visible light.
In an organic light emitting display device, pixels each including an OLED are arranged in a matrix and the brightness of each pixel is adjusted according to a gray level of video data. Each pixel may include a driving element, e.g., a driving thin film transistor (TFT), for controlling a driving current flowing in the OLED according to a voltage applied between a gate electrode and a source electrode thereof. The OLED and the driving TFT are changed in electrical characteristics due to temperature or degradation. If the electrical characteristics of the OLED andor the driving TFT differ in pixels, the brightness of pixels varies with respect to the same video data, making it difficult to implement a desired image.
In order to compensate for a change in electrical characteristics regarding the OLED and the driving TFT, an external compensation technique is known. According to an external compensation technique, when a change in electrical characteristics of the OLED or the driving TFT is sensed, the sensing value is stored in a memory and digital video data is modulated by a compensation value based on the sensing value. The sensing and compensating operation may be frequently performed under the control of a timing controller while an organic light emitting display device is being driven. The timing controller may control a write operation regarding the memory to write a new sensing value in a first region of the memory, thus updating the sensing value. The timing controller may read out a compensation value stored in a second region of the memory by controlling a read operation regarding the memory.
The sensing value stored in the memory represents a degree of degradation of a panel, a dark spot, a line dim, or panel characteristics. For example, in a case in which a display panel is degraded and a compensation process is not applied, a degradation pattern as illustrated in FIG. 1 overlaps a display image so as to be visible, and such a degradation pattern is reflected in the sensing value and stored in a memory. Here, as illustrated in FIG. 2, the sensing value stored in the memory has a form similar to the degradation pattern of FIG. 1.
The memory may be a flash type general-purpose integrated circuit (IC), and thus, every one may read out information stored in the memory. In particular, when data of the memory is divided to a size corresponding to the resolution of a display panel, information regarding a state of the display panel may be easily analyzed. A method for protecting panel state information stored in a memory would be beneficial.